Molding die for molding a component of magnetic tape cartridge

ABSTRACT

A molding die for molding a magnetic tape cartridge case in which an electronic part for exchanging a signal with the outside via contacts is incorporated as the need arises is such that a molding die portion for use in molding openings for exposing the contacts of the electronic part is constituted of two kinds of inserts which are alternatively attachable to the molding die proper; and a first insert is used to form openings for exposing the contacts, whereas a second insert is used to shut the openings for exposing the contacts.

BACKGROUND OF THE INVENTION

The present invention relates to a molding die for a component ofmolding a magnetic tape cartridge case. In particular, the presentinvention relates to a magnetic tape cartridge in which an electronicpart (e.g. an IC board) for storing information as to managing recordedcontents apart from a recording magnetic tape is incorporated as theneed arises. In addition, the present invention also relates to amolding die for molding a magnetic tape cartridge having a lidstructure.

Heretofore, a magnetic tape cartridge disclosed in Japanese PatentUnexamined Publication No. Sho. 63-168889 is already known, in whichcartridge an electronic part (hereinafter referred to as, for example,an IC board as the IC board is often employed) for storing informationas to managing recorded contents apart from a recording magnetic tape isincorporated, so that signals are exchanged between a record reproducingapparatus (e.g., hardware such as a tape recorder) and the IC board viaits contacts which are exposed outside.

In this case, a cartridge case is provided with openings for use inexposing to the outside the contacts of the IC board incorporated in thecartridge case. When the IC board is incorporated in the cartridge case,the contacts of the IC board shut the inside openings, whereby thecontacts on the hardware side can be brought into contact with thecontacts of the IC board from the outside.

The aforementioned IC board is incorporated in such a cartridge caseonly when it is required and not incorporated therein when it is notrequired. Therefore, the openings are left open when the IC board is notincorporated and this may cause the contacts on the hardware side to bestuck in the openings.

Consequently, a dummy board instead of the IC board is normallyincorporated so as to shut the openings from the inside.

In a case where a dummy board is used, the dummy board needs to be newlyprepared as a part though a cartridge case remains to be used as acommon part and this results in increasing the number of parts andnecessitating the work of incorporating the dummy board, thus causing anincrease in the cost of production. This is a problem.

In addition to this, with the recent technological innovation inincreasing the density of magnetic recording media, magnetic tapecartridges, video tape recorders (hereinafter called “VTRs”) and thelike are increasingly made compact. Consequently, VTRs tend to becomefrequently used outdoors for taking photographs of landscapes, personsand the like.

For the reason stated above, there has been put to practical use amagnetic tape cartridge having two to three pieces of lids for coveringthe whole surface and undersurface of a magnetic tape so as to protectthe magnetic tape from dust in consideration of the use of such amagnetic tape cartridge outdoors.

A description will subsequently be given of a conventional magnetic tapecartridge with reference to the accompanying drawings.

As shown in a perspective assembly drawing of FIG. 1, a magnetic tape114 is stretched over the front of a magnetic tape cartridge 113 andwhile the magnetic tape 114 is not used, it is covered with an outer lid115, a top lid 116 and an inner lid 117.

FIGS. 2 and 3 show a perspective and a sectional view of the lidportion, respectively.

The outer lid 115 has an outer lid portion 115 a for covering the frontof the magnetic tape 114 stretched in an opening portion 120, and sideplates 115 b for covering the front sides of an upper and a lower half118, 119. The side plates 115 b have a pair of fulcrum pins 115 c, whichare respectively inserted in a pair of notched portions provided in bothfront side portions of the upper half 118. The outer lid 115 is setrotatable around the fulcrum pins 115 c. Further, a pair of pin holes115 d are made in the upper fronts of the side plates of the outer lid115.

The top lid 116 has a top lid portion 116 a for covering the upper edgeof the magnetic tape 114 stretched in the opening portion 120, and sideplates 116 b for covering the side faces of the upper half 118. A pairof support pins 116 c are provided on the side plates 116 b of the toplid 116 and rotatably inserted into the pin holes 115 d of the outer lid115.

A pair of thin-wall portions that have been made as thin as the sideplates 116 b are provided on the respective front side faces of theupper half 118. Further, a pair of grooves for guiding the top lid areformed in the respective thin wall portions, and a pair of guide pins116 d formed on the rear insides of the side plates 116 b are slidablymounted in the respective grooves.

A pair of bracket portions 116 e are provided on the inside of the toplid 116, and pin holes 116 f are formed in the respective bracketportions 116 e.

FIG. 4 is a perspective view of the inner lid 117.

The inner lid 117 has an inner lid portion 117 a for covering theundersurface of the magnetic tape 114 stretched in the opening portion120, and side plates 117 b. A pair of support pins 117 c are provided onthe respective side plates 117 b of the inner lid 117 and rotatablyinserted into the respective pin holes 116 f of the bracket portions 116e of the top lid 116. Further, the lower side faces of the inner lid 117are equipped with a pair of protrusions 117 d, which are formed withguide pins 117 e, respectively.

A pair of inner lid guide grooves whose top portions are opened areprovided in the rear of a pair of tape guides formed in the lower half119 and both side faces of the opening portion 120, and the pair ofguide pins 117 e formed on the protrusions 117 d of the inner lid 117are slidably inserted into the inner lid guide grooves.

A process for molding the inner lid 117 thus structured willsubsequently be described. As shown in FIG. 5, a cavity 121 for use inmolding the inner lid 117 includes a movable metal mold unit 122 and astationary metal mold unit 123.

The movable metal mold unit 122 and the stationary metal mold unit 123are placed opposite to each other so that mold breaking and clamping canbe carried out by the locking unit of a molding machine, and in such astate that both of them have been clamped together, the cavity isformed. When the cavity 121 is filled with molten resin under pressureby an injection molding machine in such a clamped state before themolten resin is cooled and solidified, the inner lid 117 is formable.

Magnetic tape cartridges are classified into two categories; namely, forgeneral use and for business use and those in both categories aresimilar in construction except that the inner lids for use in the formerare longitudinally shorter than those for use in the latter. When thesetwo kinds of inner lids are manufactured, however, the inner-lid moldingmethod that has conventionally been adopted comprises the steps ofpreparing a special die for each type and setting the special die in amolding machine in agreement with the type of manufacture. In themolding method like this, troublesome work of removing the molding diefrom the molding machine, disassembling and assembling the die, mountingthe die in the molding machine and so on has to be repeated in ordereach time the type of manufacture is changed, thus causing the rate ofoperation to be extremely lowered. Moreover, the cost of equipment tendsto increase because kinds of dies to be prepared also increases, whichresults in incurring an increase in the cost of production. This is alsoa problem.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide amolding die for molding a component of magnetic tape cartridge which cansolve the foregoing problem.

It is an object of a first aspect of the present invention to provide amolding die for molding two kinds of magnetic tape cartridge cases, oneof which has openings for use in exposing contacts to the outside andthe other one has no openings therefor in order to minimize the cost formolding them, so that a dummy board can be dispensed with.

In addition, it is also an object of a second aspect of the presentinvention to curtail the cost of manufacturing molding dies by employingthe die commonly for molding lids so as to effect improvement in therate of productive operation.

In order to accomplish the aforesaid object of the present invention, amolding die for molding a magnetic tape cartridge case in which anelectronic part for exchanging a signal with the outside via contacts isincorporated as the need arises, comprising:

a first and second mold units defining a mold cavity for at least partof the cartridge case; and

a first and second inserts alternatively attachable to at least one ofthe first and second mold units for forming an opening which exposes thecontacts of the electronic part,

wherein the first insert is used to form openings for exposing thecontacts, whereas the second insert is used to shut the openings forexposing the contacts.

In the above-mentioned molding die for molding a magnetic tape cartridgecase, the second mold unit preferably has a recess portion capable ofreceiving the first and second inserts.

In addition, in the above-mentioned molding die for molding a magnetictape cartridge case, the first and second inserts may be alternativelyattached to the recess of the second mold unit by a screw.

With the arrangement stated above, the molding die for molding a casewith the first insert is set in the molding die proper when anelectronic part is incorporated in the case. Thus, the case formed withopenings is obtainable. The molding die for molding a case with thesecond insert is set in the molding die proper when no electronic partis incorporated in the case. Thus, the case formed without openings isobtainable.

In order to solve the foregoing problems, a molding die for molding amagnetic tape cartridge lid comprising an outer lid, a top lid and aninner lid which are used for covering a magnetic tape is such that:

a portion of the die for molding one end of the lid in the longitudinaldirection of the lid is formed with an insert type die; and the inserttype die comprises a number of inserts members are alternativelyselected and loaded in accordance with a length of the lid in thelongitudinal direction.

In order to solve the foregoing problems, further, a molding die formolding a magnetic tape cartridge lid comprising an outer lid, a top lidand an inner lid which are used for covering a magnetic tape is suchthat:

a portion of the die for molding one end of the lid in the longitudinaldirection of the lid is formed with a slide core capable of adjustingmolding length in the longitudinal direction of the lid; and the slidecore is located in a desired position in the longitudinal direction forinjection molding.

Further, the foregoing problem can be solved by a molding die, accordingto the present invention, for molding at least two kind of magnetic tapecartridge lids, the lids having a different length in a longitudinaldirection thereof, comprising:

a stationary mold unit;

a movable mold unit movable relative to the stationary mold unit;

a first insert attached to at least one of the stationary molding unitand the movable mold unit, in which a molding cavity for a shorterlength lid is defined by a combination of the stationary mold unit, themovable mold unit and the first insert, and the first insert has arecess corresponding with a part of the molding cavity for molding oneend of the shorter length lid in the longitudinal direction thereof; and

a second insert attached to at least one of the stationary molding unitand the movable mold unit, in which a molding cavity for a longer lengthlid is defined by a combination of the stationary mold unit, the movablemold unit and the second insert, and the second insert has a recesscorresponding with a part of the molding cavity for molding one end ofthe longer length lid in the longitudinal direction thereof;

in which the first insert and the second insert are alternativelyattached to the at least one of the units.

Furthermore, in the above-mentioned molding die, the first insert isonly different from and the second insert in a depth of the recess,preferably.

Moreover, in the above-mentioned molding die, the magnetic tapecartridge lid may be selected from a group consisting of an outer lid, atop lid and an inner lid by which a lid assembly for covering a magnetictape is constituted.

In addition, in the above-mentioned molding die, in which the magnetictape cartridge lid is the inner lid.

Still furthermore, the object can be attained by a molding die,according to the present invention, for molding at least two kind ofmagnetic tape cartridge lids, the lids having a different length in alongitudinal direction thereof, comprising:

a stationary mold unit;

a movable mold unit movable relative to the stationary mold unit; and

a slide core disposed at one end of a molding cavity which is defined bya combination of the stationary mold unit, the movable mold unit and theslide core, the slide core being movable in the longitudinal directionbetween a first position forming a shorter molding cavity for a shorterlength lid between the stationary mold unit and the movable mold unitand a second position forming a longer molding cavity for a longerlength lid between the stationary mold unit and the movable mold unit.

In the above-mentioned molding die, the magnetic tape cartridge lid maybe selected from a group consisting of an outer lid, a top lid and aninner lid by which a lid assembly for covering a magnetic tape isconstituted.

In the above-mentioned molding die, in which the magnetic tape cartridgelid is preferably the inner lid.

In the case of an insert type die according to the present invention,the length of a cavity is made changeable by loading a desired inserttype die, so that a lid having desired length becomes moldable. In thecase of a die with the slide core, the length of a cavity is madechangeable by locating the slide core in a desired position, so that alid having desired length becomes moldable.

The nature, utility and principle of the invention will be more clearlyunderstood from the following detailed description and the appendedclaims when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective assembly drawing of a magnetic tape cartridge inthe prior art.

FIG. 2 is a perspective view of a lid portion in the prior art.

FIG. 3 is a sectional view of the lid portion in the prior art.

FIG. 4 is a perspective view of an inner lid.

FIG. 5 is a sectional view of a molding die for molding a conventionalinner lid.

FIGS. 6(a) and 6(b) are plan views of the principal part of a casemolding die embodying the present invention: FIG. 6(a) refers to a casewhere a first insert is mounted in the molding die so as to formopenings; and FIG. 6(b) refers to a case where the second insert ismounted therein so as to shut the openings.

FIGS. 7(a) and 7(b) are plan views of the principal part of the lowerhalf of a cartridge case which is molded by the use of the molding dieof FIG. 6: FIG. 7(a) refers to a case where the openings are formed; andFIG. 7(b) refers to a case where openings are shut.

FIG. 8 is a block diagram showing the whole magnetic tape cartridge as afinal product.

FIG. 9 is an exploded perspective view of the principal part of FIG. 8.

FIG. 10 is a sectional view of the present invention.

FIG. 11(a) is a sectional view of a molding die for molding an inner lidfor general use by utilizing an insert type die according to the presentinvention; and FIG. 11(b) a sectional view of a molding die for moldingan inner lid for business use.

FIG. 12(a) A sectional view of a molding die for molding an inner lidfor general use by utilizing a slide core according to the presentinvention; and FIG. 12(b) a sectional view of a molding die for moldingan inner lid for business use.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings, there is given a detaileddescription of a first embodiment of the present invention.

FIG. 6 is a plan view of the principal part of a case molding dieembodying the present invention; FIG. 7, a plan view of the principalpart of the lower half of a cartridge case which is molded by the use ofthe die; FIG. 8, a block diagram showing the whole magnetic tapecartridge as a final product; and FIG. 9, an exploded perspective viewof the principal part of FIG. 8.

Referring to FIG. 8 first, there is given a description of a magnetictape cartridge M.

The magnetic tape cartridge M contains a magnetic tape (not shown) in acartridge case 1 as a resin molded product. The cartridge case 1 has alower half 2 (as one of cartridge case half) and an upper half 3 (as theother of cartridge case half) and on one end sides of their rear endwalls 2 a, 3 a exist a control data storage portion 5 for storing, forexample, information as to managing recorded contents of the magnetictape and an erasure-error preventive portion 6. The erasure-errorpreventive portion 6 has an erasure-error preventive leaf 20 whose pawlportion is exposed to the outside from a hole 21 provided in the rearend wall 3 a of the upper half 3.

The control data storage portion 5 is provided as the need arises andnot provided when it is unnecessary. In the magnetic tape cartridge Mshown in FIG. 8, there is provided the control data storage portion 5 byincorporating an IC board (an electronic part) in the rear end wall 2 aof the cartridge case 1. In the rear end wall 2 a of the lower half 2,there are also provided openings 11 for exposing to the outside aplurality of contacts 12 of the IC board 10 in such a way as tocorrespond to the contacts 12.

FIG. 9 is a perspective exploded view with the aforementioned partialcutaway control data storage portion 5 intended to make the control datastorage portion easily understandable. The IC board 10 includes acircuit 14 and the contacts 12 which are provided in a base plate 13 andis fitted into a housing space 15 which is arranged along the rear endwall 2 a of the lower half 2. In such a state that the IC board 10 hasbeen thus fitted, its contacts are exposed to the outside through theopenings 11 provided in the rear end wall 2 a of the lower half 2.Consequently, contacts on the hardware side can be brought into contactwith the contacts 12 through the openings 11. In this case, the rearside of the housing space 15 is partitioned by an elastic wall 16 andthe error-erasure preventive leaf (illustration omitted) is placedbehind the elastic wall 16.

Although the IC board 10 is incorporated in the cartridge case 1 of themagnetic tape cartridge M to provide the control data storage portion 5,there is also a magnetic tape cartridge of such a type as is providedwith no control data storage portion 5. In this case, it is inconvenientto leave the contact exposure openings 11 open in the rear end wall 2 aof the lower half 2.

A molding die for molding a case provided according to this embodimentof the present invention is such that two kinds of lower halves 2 withthe openings 11 left open and the openings 11 kept shut are molded.

FIG. 6 shows the molding die for molding a case according to thisembodiment of the present invention. This molding die comprises a lowermold unit 31, a upper mold unit 32 and two kinds of inserts 33A, 33B.The two kinds of inserts 33A, 33B correspond to molding die portions forforming the openings of the lower half 2 and are alternatively set in arecess 38 formed in the lower mold unit 31 and fixed in position with afixing screw 34. FIG. 6(a) refers to a case where the first insert 33Ais mounted in the lower mold unit 31 and FIG. 6(b) refers to a casewhere the second insert 33B is mounted in the lower mold unit 31. Thefirst insert 33A is different from the second insert 33B in that onlythe dimensions of projections of front edge faces 41A, 41B are varied.

The first insert 33A is mounted in the lower mold unit 31 when a lowerhalf 2A having the openings 11 as shown in FIG. 7(a) is formed and whilethe first insert 33A is mounted therein as shown in FIG. 6(a), the frontedge face 41A is brought into contact with the edge face of the uppermold unit 32, whereby a gap allowing resin to penetrate into the contactportion is eliminated. Thus, the lower half 2A of a type having theopenings 11 as shown in FIG. 7(a) is made formable by injecting resininto a cavity.

Further, the second insert 33B is mounted in the lower mold unit 31 whenthe lower half 2A having the openings 11 which are shut with closingwalls 11B is formed and while the second insert 33B is mounted thereinas shown in FIG. 6(b) whereby to secure the gap allowing resin topenetrate between the front edge face 41B and the edge face of the uppermold unit 32. Thus, the lower half 2A of a type having the closedopenings 11 as shown in FIG. 7(b) is made formable thereby.Consequently, a dummy board can be dispensed with when the IC board isnot incorporated in the magnetic tape cartridge and the use of the lowerhalf 2B of this type instead has the effect of reducing the cost to theextent that the dummy board is not employed.

With the molding die constituted of the lower mold unit 31 and the uppermold unit 32, the inserts 33A, 33B are alternatively mounted in themolding die according to the desired type of a molded product, wherebythe lower half 2A with the openings opened and the lower half 2B withthe openings closed can be molded simply with the preparation of onlytwo kinds of inserts 33A, 33B. Thus, an increase in the cost ofproducing molding dies can be minimized.

As set forth above, the two kinds of cartridge cases with the openingsopened and the openings closed are made obtainable simply by preparingonly two kinds of inserts and mounting one of them alternatively in themolding die according to the present invention. Therefore, theproduction cost can be reduced by dispensing with a dummy board withoutpreparing two kinds of molding dies.

Hereinafter, referring to the accompanying drawings of FIGS. 10-12(b),there is given a description of the present invention. Incidentally, adescription of the structure of an inner lid will be omitted as thestructure thereof is similar to what is shown with reference to theconventional example.

A die having an insert type die as a second embodiment of the presentinvention will be described first. As shown in FIG. 10, a cavity 101 formolding an inner lid used for forming a tape cartridge includes amovable metal mold unit 102 and a stationary metal mold unit 103. Themovable metal mold unit 102 is fitted to the movable platen of a moldingmachine (not shown) via a die plate (a bottom plate). The stationarymetal mold unit 103 forming a pair with the movable metal mold unit 102is fitted to the fixed platen of the molding machine (not shown) via adie plate (a front plate). The molding length (cavity length) a of thestationary metal mold unit 103 is constant and by loading an insert-typedie loading portion 104 with insert type dies 105 a, 105 b different inmolding length, cavities different in length can be formed separately.

The movable metal mold unit 102 and the stationary metal mold unit 103are set opposite to each other so that mold breaking and clamping can becarried out by the locking unit of the molding machine, and in such astate that both of them have been clamped together, the cavity isformed. When the cavity 101 is filled with molten resin under pressureby an injection molding machine in such a clamped state before themolten resin is cooled and solidified, the inner lid is formable.

FIG. 11(a) shows a molding die for molding the inner lid of a DVC(Digital Video Cassette) for general use. The length of the inner lidfor general use in the longitudinal direction is a +b. A cavity having alength of a +b is formed by loading the insert type die 105 a with amolding portion having a length of b into the insert-type die loadingportion 104. The insert type die 105 a is used to mold one side platewhich is provided with the support pin of the inner lid, a protrusionand a guide pin.

FIG. 11(b) shows a molding die for molding the inner lid of a DVC forbusiness use. The inner lid of the DVC for business use and the innerlid of the DVC for general use are different only in longitudinallength. The movable metal mold unit 102 and stationary metal mold unit103 for business use are the same as those for general use. Thelongitudinal length of the inner lid for business use is a +c. A cavityhaving a length of a +c is formed by loading the insert type die 105 bwith a molding portion having a length of c into the insert-type dieloading portion 104 and the insert type die 105 b is used to mold theside plate of the inner lid. Thus, the longitudinal length of the cavityis made changeable only by replacing the insert type die. Since it ispossible to mold inner lids different in length, the movable metal moldunit 102 and the stationary metal mold unit 103 can be employed forcommon use.

A die equipped with a slide core as a third embodiment of the presentinvention will subsequently be described. FIG. 12(a) shows a molding diefor molding an inner lid for general use. The longitudinal length of theinner lid for general use is d (=a+b) and the length d of a cavity isset by adjusting the position of a slide core 106 provided between themovable metal mold unit and the stationary metal mold unit. The slidecore 106 is used to mold one of the side plates of the inner lid.

FIG. 12(b) shows a molding die for molding an inner lid for businessuse, which is different from what is for general use in onlylongitudinal length. The movable metal mold unit and stationary metalmold unit for business use are the same as those for general use. Thelongitudinal length of the inner lid for business use is e (=a+c) and itis also possible to mold the side plate of the inner lid only bychanging the sliding quantity of the slide core for general use to thesliding quantity of the slide core 106 for business use, which isprovided between the movable metal mold unit and the stationary metalmold unit. Since the inner lids different in longitudinal length is mademoldable only by changing the sliding quantity of the slide core 106,the rest can be employed for common use.

Although a description has been given of the exemplary embodiments ofthe present invention, the use of the molding dies according to thepresent invention is not limited to molding the two kinds of inner lids,namely, for general use and for business use but applicable to moldingvarious lids different in longitudinal length.

As set forth above, a portion of the die for molding one end of the lidin the longitudinal direction of the lid is formed with the insert typedie, and the insert type die corresponding to molding length in thelongitudinal direction of the lid is selected and load for injectionmolding; or otherwise a portion of the die for molding one end of thelid in the longitudinal direction of the lid is formed with the slidecore capable of adjusting molding length in the longitudinal directionof the lid, and the slide core is located in a desired position in thelongitudinal direction for injection molding. Consequently, anotherportion of the die for molding the other end of the lid is commonlyusable for molding lids having various kinds of length. Therefore, thedie can be used commonly for molding lids with the effect of improvingthe rate of productive operation and making it possible to curtail thecost of manufacturing molding dies.

While there has been described in connection with the preferredembodiment of the invention, it will be obvious to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the invention, and it is aimed, therefore, to cover inthe appended claim all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:
 1. A molding die for molding at least two kinds ofmagnetic tape cartridge lids, said lids having a different length in alongitudinal direction thereof, comprising: a stationary mold unit; amovable mold unit movable relative to said stationary mold unit; one ofa first insert and a second insert attached to a portion of at least oneof said stationary molding unit and said movable molding unit, whereinsaid first insert attached to said portion of at least one of saidstationary molding unit and said movable mold unit defines a moldingcavity for a shorter length lid, and said first insert has a recesscorresponding with a part of said molding cavity for molding one end ofsaid shorter length lid in the longitudinal direction thereof whereinsaid second insert attached to said portion of at least one of saidstationary molding unit and said movable mold unit defines a moldingcavity for a longer length lid, and said second insert has a recesscorresponding with a part of said molding cavity for molding one end ofsaid longer length lid in the longitudinal direction thereof; andwherein said first insert and said second insert are alternativelyattached to said portion of said at least one of said stationary moldunit and said movable mold unit.
 2. The molding die according to claim1, in which said recess of said first insert is not as deep as saidrecess of said second insert.
 3. The molding die according to claim 1,in which said magnetic tape cartridge lid is selected from a groupconsisting of an outer lid, a top lid and an inner lid by which a lidassembly for covering a magnetic tape is constituted.
 4. The molding dieaccording to claim 1, in which said magnetic tape cartridge lid is saidinner lid.
 5. A molding die for molding at least two kinds of magnetictape cartridge lids, said lids having a different length in alongitudinal direction thereof, comprising: a stationary mold unit; amovable mold unit movable relative to said stationary mold unit; and aslide core disposed at one end of a molding cavity which is defined by acombination of said stationary mold unit, said movable mold unit andsaid slide core, said slide core being movable in the longitudinaldirection between a first position forming a shorter molding cavity fora shorter length lid between said stationary mold unit and said movablemold unit and a second position forming a longer molding cavity for alonger length lid between said stationary mold unit and said movablemold unit.
 6. The molding die according to claim 5, in which saidmagnetic tape cartridge lid is selected from a group consisting of anouter lid, a top lid and an inner lid by which a lid assembly forcovering a magnetic tape is constituted.
 7. The molding die according toclaim 5, in which said magnetic tape cartridge lid is said inner lid.